The most important biotechnological advances made in the 20th century involved methods that convert a single DNA molecule into a population of identical DNA molecules. The first wave of techniques for this purpose employed cells (cloning) and the second wave employed PCR. Cloning was advantageous in that the populations emanating from individual molecules were inherently separated through this process. In contrast, PCR-based methods required individual compartments (tubes) for each template if the products were to be kept separate. Emulsion PCR overcame this disadvantage by miniaturizing the compartments so that millions of templates could be individually amplified within a single tube.
BEAMing (beads, emulsions, amplification, and magnetics) built on emulsion PCR by keeping products formed within each compartment together once the emulsions were broken. This was accomplished through (i) inclusion of beads within the compartments and (ii) ensuring that one strand of the PCR product is bound to the beads. After amplification, each bead is coated with thousands of copies of the single DNA molecule present in the compartment that contained that bead and these beads could easily be recovered with a magnet or by centrifugation.
Beads obtained via BEAMing accurately reflect the DNA diversity present in the template population and can be used to determine what fraction of a DNA population contains a specific mutation. Because each bead contains thousands of molecules of the identical sequence, the signal to noise ratio obtained with hybridization or enzymatic assays is extremely high. Millions of beads can be analyzed within minutes using conventional flow cytometry or optical scanning instruments. The DNA bound to the beads also provides excellent templates for high-throughput sequencing.
There is a continuing need in the art to improve the throughput of DNA amplification to improve analysis of DNA and genetic diagnoses.